- Add an Expires Header
	- Bât mod_expires trong httpd.conf
	  LoadModule expires_module modules/mod_expires.so
	- Nếu thành công trên HTTP request sẽ thấy response trả về: Expires Thu, 12 Dec 2013 06:13:11 GMT
	- The first time someone visits your site, their browser will fetch all your images, css files, javascript files, etc. 
	  Normally that happens every time the same visitor comes back to your site.
	- With Expires headers you tell your website visitor’s browser that the files you specify are not changing until after a certain time, for example a month.
	- if you set your javascript to 1 year, and you update one of your javascript files, you’d have to rename the actual file. A good way to do this is by versioning, i.e. myfile_v1.2.js
	- Note: Để ý Request Headers nếu thấy Cache-Control max-age=0 tức là browwer gửi thông tin lên server là không cache

- Gzip Components	
	- Bật mod_expires trong httpd.conf
	  LoadModule deflate_module modules/mod_deflate.so
	- Nếu thành công trên HTTP request sẽ thấy response trả về: Content-Encoding gzip

- Reduce DNS Lookups
	- It typically takes 20-120 milliseconds for DNS to lookup the IP address for a given hostname
	- Most browsers have their own caches, separate from the operating system's cache
	- Reducing the number of unique hostnames has the potential to reduce the amount of parallel downloading that takes place in the page.
	=> Avoiding DNS lookups cuts response times, but reducing parallel downloads may increase response times.
	=> My guideline is to split these components across at least two but no more than four hostnames. 
	   This results in a good compromise between reducing DNS lookups and allowing a high degree of parallel downloads.

- Minify JavaScript
	JSMin was used to minify the script. 
	The Dojo Compressor was used to obfuscate the script. 

- Configure ETags
    - If you host your web site on just one server, this isn't a problem.
    - In Apache, this is done by simply adding the following line to your Apache configuration file:
      FileETag none





Ko uu tien
Content delivery network (CDN)